It is desirable, for vehicle strengthening members, to maximize impact energy absorption and bending resistance while minimizing mass per unit length of the strengthening member. Impact energy absorption may be maximized, for example, by assuring that the strengthening member compacts substantially along a longitudinal axis of the strengthening member upon experiencing an impact along this axis. Such longitudinal compaction may be referred to as a stable axial crush of the strengthening member.
When a compressive force is exerted on a strengthening member, for example, by a force due to a front impact load on a vehicle's front rail or other strengthening member in the engine compartment, the strengthening member can crush in a longitudinal direction to absorb the energy of the collision. In addition, when a bending force is exerted on a strengthening member, for example, by a force due to a side impact load on a vehicle's front side sill, B-pillar or other strengthening member, the strengthening member can bend to absorb the energy of the collision.
Conventional strengthening members rely on increasing the thickness and hardness of side and/or corner portions to improve crush strength. However, such increased thickness and hardness increases weight of the strengthening member and reduces manufacturing feasibility. It may be desirable to provide a strengthening assembly configured to achieve the same or similar strength increase as provided by the thickened sides and/or corners, while minimizing mass per unit length of the member, and maintaining a high manufacturing feasibility.
It may further be desirable to provide a strengthening member that can achieve increased energy absorption and a more stable axial collapse when forces such as front and side impact forces are exerted on the strengthening member, while also conserving mass to reduce vehicle weights and meet emission requirements. Also, it may be desirable to provide a strengthening member that can achieve improved energy absorption and bend when a bending force is exerted on the strengthening member. Additionally, it may be desirable to provide a strengthening member that possesses improved noise-vibration-harshness performance due to work hardening on its corners. In addition, it may be desirable, to provide a tunable strengthening member cross section configured to achieve strength increases (i.e., load carrying and energy absorption) over basic polygonal designs, while also allowing flexibility in design to meet a range of vehicle applications.